A force detection device including a mesa gauge has been developed, examples of which are disclosed in Patent Literatures 1 through 3. A mesa gauge has a piezoresistive effect and an electric resistance value varies with stress. The force detection device is configured to detect a force by exploiting a variance in electrical resistance value.
A force detection device exploiting a piezoresistive effect has been developed, an example of which is disclosed in Patent Literature 1. The force detection device of such a type includes a substrate and a force transmission block. Multiple mesa gauges forming a bridge circuit are provided to a principal plane of the substrate. For example, the multiple mesa gauges forming the bridge circuit are disposed correspondingly to sides of a rectangle. The force transmission block is provided to be in contact with top surfaces of the multiple mesa gauges. When the force transmission block presses the mesa gauges, compressive stress applied to the mesa gauges increases, which causes electric resistance values of the mesa gauges to vary by the piezoresistive effect. A force applied to the force transmission block is detected from a variance in electric resistance value.
Patent Literature 2 proposes a force detection device having a sealing structure in which a force transmission block is joined to a substrate to surround all around multiple mesa gauges. Such a sealed force detection device is capable of having highly-sensitive characteristics because a force applied to the force transmission block is effectively transmitted to the multiple mesa gauges.
In the sealed force detection device, compressive stress applied to the mesa gauges depends on positions of the mesa gauges in a space where the mesa gauges are sealed (hereinafter, referred to as the sealing space). Accordingly, in order to apply compressive stress appropriately to the mesa gauges, it is necessary to dispose the mesa gauges at predetermined positions in the sealing space. In a case where multiple mesa gauges disposed correspondingly to sides of a rectangle form a bridge circuit, a length of each mesa gauge is automatically determined and sensitivity of the mesa gauges can be adjusted only by changing a width of the mesa gauges. Hence, design flexibility of the mesa gauges is low.